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2011/11/14

Galactic Astronomy 銀河物理学特論 I Lecture 1-6: Multi-wavelength properties of galaxies Seminar: Draine et al. 2007, ApJ, 663, 866 Lecture:. 2011/11/14. Extinction (scattering + absorption) by dust. UV radiation is absorbed by dust, optical radiation is scattered by dust.

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2011/11/14

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  1. Galactic Astronomy銀河物理学特論 ILecture 1-6: Multi-wavelength properties of galaxiesSeminar: Draine et al. 2007, ApJ, 663, 866 Lecture: 2011/11/14

  2. Extinction (scattering + absorption) by dust. UV radiation is absorbed by dust, optical radiation is scattered by dust.

  3. Thermal emission from dust. Absorbed energy from UV radiation is thermally emitted in the MIR and FIR wavelength range. Blue: (3.6um) Green: (4.5um) Red: PAH dust emission at 8um.

  4. Infrared emission from galaxies: Mid-Far infrared emission of galaxies is dominated by thermal emission from dust components. The figure below shows the dust emission from the Galaxy observed as a thermal background radiation in the infrared wavelength range. Break down model is shown with lines. Li & Draine 2001, ApJ, 554, 778 Hollenback & Tielens 1991

  5. Thermal emission from dust. Map of Galactic dust emission made by IRAS + COBE/DIRBE. Shown in Galactic coordinate. Northern hemisphere. Schlegel, Finkbeiner, Davis, ApJ, 500, 525

  6. SED models for NGC1569: Models for emission from dust and extinction by dust. PAH: Very Small Grains: 1.2nm<a<15nm Big Grains: 15nm<a<110nm Galliano et al. 2003, A&A, 407, 159

  7. SED models for ULIRGs: Models for emission from dust for Ultra Luminous InfraRed Galaxies. Cold (red) dust with T=40K “Cirrus” component. Warm (green) dust with T=100-200K Hot (purple) dust with up to T=1,000K Sometimes heated by active nucleus. Ultraluminous Infrared Galaxies Armus et al. 2007, ApJ, 656, 148

  8. PDR ?: Photo-Dissociate (解離)Region. Molecules are photo-dissociated by strong UV radiation near bright O,B stars (ex. Orion bright bar region). Diffuse ISMs also have similar conditions to the dense PDRs. Strong [CII] 158um and [OI] 63um emission Draine & Bertoldi 1999

  9. FIR emission: Basically black body radiation from large grains dominate the wavelength range. Large grains are at thermal equilibrium with the UV radiation in the inter-stellar field. Small grains (<100A) are not at the thermal equilibrium under typical UV radiation field. Draine 2003, ARAA, 41, 241 Li & Draine, 2001, ApJ, 554, 778

  10. MIR emission: Emission from PAHs Emission lines from PAHs (Polycyclic aromatic hydrocarbon molecules) are prominent in the MIR wavelength range. MIR spectra of Orion nebular bar region. Allamandola et al. 1999, ApJL, 511, 115 “Unidentified Infrared Bands”: Peeters 2003, astro-ph/0312184

  11. MIR emission: Dust continuum, up to T=1000K (dust sublimation temperature, dust destruction). PAH emission, Silicate absorption line, forbidden lines from Ne, Ar, etc. Ultraluminous Infrared Galaxies Armus et al. 2007, ApJ, 656, 148

  12. MIR emission line diagnostics: Ultraluminous Infrared Galaxies Armus et al. 2007, ApJ, 656, 148

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